Acute Sodium-Retaining Effects of Estrogens in Dogs 1

Abstract

Summary

Five conscious adrenalecto-mized dogs on a high-sodium diet Received iv injections of 650 μg of estradiol, 650 μg of estriol, or vehicle alone. Every animal Received each of the three injections on separate days. One hour prior to and 4 hr following the injection, the urinary excretion rates of Na and K, creatinine clearances, and plasma Na and K concentrations were determined. After administration of estradiol, the urinary Na excretion decreased from 154 ± 7 (SEM) to 63 ± 7 μequiv/min (P < 0.01); urinary K excretion also declined from 22 ± 4 to 10 ± 4 μequiv/min (P < 0.05). Following the injection of estriol, urinary Na excretion fell from 139 ± 8 to 56 ± 16 μequiv/min (P < 0.01), while urinary K excretion decreased from 21± 2 to 9 ± 3 μequiv/min (P < 0.01). Administration of the vehicle alone did not alter the rate of urinary excretion of Na or K. No detectable changes in creatinine clearance occurred following administration of estrogens or the vehicle. Plasma Na concentration remained unaltered, but plasma K declined slightly in all experiments. These studies demonstrated that estrogens administered iv require 2-4 hr for pronounced effects on urinary Na and K excretion, and that the acute Na-retaining effects of estrogens are not mediated by adrenal steroids or by decreases in glomer-ular filtration rate.

Surgical assistance was provided by Mr. Charles Payne, Mr. Jerry Benedict, and Mr. Dale Welch. Creatinine determinations were performed by Ms. Rebecca Wright.